Fuel compositions



Patented July 4, 1950 FUEL COMPOSITIONS Aaron Wachter and Nathan Stillman, Berkeley,

Calii'., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 31, 1948, Serial No. 47,133

8 Claims.

This invention relates to novel fuel compositions. More specifically, this invention pertains to gasoline fuels for spark ignition internal combustion engines containing therein an additive having the property, inter alia, of reducing combustion chamber deposits.

The deleterious effects of combustion chamber deposits in internal combustion engines are well known. For example, in spark ignition internal combustion engines, especially those operating on gasolines containing tetra-ethyl lead, deposits are formed which adhere to the various parts, such as the spark plugs, valve stems, piston crown, and the like, of the engine'which come in contact with the combustion products of such fuels (gasolines), resulting in failure or deterioration, or both, of the affected parts. Scavenging agents, such as ethylene dibromide, normally added to leaded fuels, aid in preventing such deposition, but no such agent is known which even substantially solves the deposition problem. Engines which operate on non-leaded fuels also suffer from deposition (of the products of combustion) on the various parts of the engine, especially in the combustion chamber. Although the nature of the deposits varies according to the fuel composition employed, e. g., in spark ignition internal combustion engines operating on leaded gasoline the deposits contain a substantial portionpf lead compounds, while in spark ignition internal combustion engines operating on non-leaded gasoline, the deposits are largely carbonaceous in nature, the deleterious effects of all types of these deposits are recognized. The use of scavenging agents, as above-mentioned, which at best are inadequate, the use of special cleaning solvents, e. g., by flooding the combustion chambers therewith, and mechanical means, such as scraping, both of which latter methods require that the engine be idle, are the chief methods used until now for combatting combustion chamber deposits.

An object of this invention is to provide fuel compositions which eliminate, or at least materially inhibit and/or reduce, the combustion chamber deposits of spark ignition internal combustion engines. Another object is to provide fuel compositions which decrease lacquer formation, ring sticking, and oil consumption. Other objects and their achievement in accordance with the present invention will be apparent from the following specification.

It has now been found that the incorporation in gasoline hydrocarbon fuels of compounds having a nitroso group attached to a nitrogen atom which in turn is attached to two hydrocarbon radicals eliminates, or at least materially reduces, combustion chamber deposits of internal combustion engines, and possesses other advantages, as hereinafter more fully described.

These compounds may be illustrated by the eneral formula:

\N--N=0 Rf wherein R1 and R2 are hydrocarbon radicals. Suitable radicals include, for example, alkyl, alkenyl, aralkyl, aryl, alicyclic or cyclo-oleflnic radicals, such as the methyl, ethyl, propyl, isopropyl, normal butyl, secondary butyl, tertiary butyl, hexyl, iso-octyl, dodecyl, cetyl, stearyl, trimethyl octadecyl, allyl, methallyl, crotyl, oleyl, cyclopentyl, methyl cyclopentyl, cyelohexyl, isopropyl cyclohexyl, endomethylene cyclohexyl, cyclopentenyl, cyclohexenyl, phenyl, tolyl, xylyl, butyl phenyl, naphthyl, anthryl, and the like. R2 may be the same or different from R1.

R1 and R2 may be connected to form a ring, together with the nitrogen atom which is also attached to the nitroso group.

Preferably, the present compounds are those wherein the total number of carbon atoms in both R1 and R2 is from about 5 to about 40, and preferably from 6 to about 20. Dicyclohexyl nitrosamine is an example of such compounds, and when incorporated in gasoline, forms therewith a preferred fuel composition of the present invention. Other compounds which illustrate the additives of the persent invention are diisopropyl nitrosamine, di-n-butyl nitrosamine, din-propyl nitrosamine, diisobutyl nitrosamine, methylpentyl nitrosamine, methylcyclohexyl nitrosamine, diphenyl nitrosamine, bis(3,3,5-trimethyl-cyclohexyi) nitrosamine, methylbenzyl nitrosamine, allylbutyl nitrosamine, n-propylcyclohexenyl nitrosamine, and the like.

As above stated, it is essential to the success of the present invention that the additives incorporated in gasoline to form the fuel compositions of the present invention have a nitroso group attached to a nitrogen atom which in turn is attached to two hydrocarbon radicals. Thus, while there is a wide latitude of choice in the selection of the hydrocarbon radicals, the limitation being that preferably the total number of carbon atoms in the molecule be at least about 5 and not more than about 40, it must be attached to a =NN=O group in order to achieve the advantages of the present invention.

In preparing the compositions of the present nvention one or more of the above-described aeisoie I compounds is incorporated in a gasoline fuel which generally has a boiling range of from about 100 F. to about 400 F. By the terms gasoline hydrocarbons, gasoline fuel, "gasolines and terms of similar import, as used herein, is meant mixtures of hydrocarbons boiling in the gasoline range, namely, from about 100 F. to about 400 F., and which are normally employed in the operation of spark ignition internal combustion engines. Preferably, the present additives are dissolved in the gasoline hydrocarbons. In order to impart substantial gasoline solubility to the present compounds, the total number of carbon atoms in R1 and R2 of the above general formula is preferably at least 5, and preferably the total number is less than about 40. However, the present nitroso compounds may be dispersed Or emulsified in the fuel where necessary or desirable, in which case emulsifying agents, such as triethanolamine oleate, the alkali .metal sulfonates, and the like, may be employed if desired. Solutizers may also advantageously be employed in some instances. The quantity .of the present additives to be incorporated in gasoline fuels may be varied between about .001 and about 1% by weight, and good results obtained therewith, but preferably from about 0.01% to about 0.3% by weight is employed, since excellent results are economically obtained therewith. However, larger or smaller amounts of the additive, or mixtures thereof, may also be used.

Other additives which impart special properties to the gasoline compositions may be incorporated in the present compositions where desirable. For example, oxidation inhibitors such as alpha naphthol may be incorporated in the compositions of the present invention without adversely affecting the action of the additives of the present invention, and the beneficial effects of such additional additives are obtained.

The following examples illustrate the compositions and process of engine operation in accordance with the present invention, which is not to be considered as limited thereby.

Example I Dicyclohexyl nitrosamine was dissolved in an 80 octane number leaded gasoline to form a 0.02% by weight solution thereof. The resulting fuel composition was compared to the same gasoline in the absence of the dicyclohexyl nitrosamine. This comparison was efiected in a Franklin aircraft engine (four cylinder spark ignition air cooled engine of 4 inch bore and 3 inch stroke) operated at 2200 R. P. M. under a load of 37 B. H. P. for 50 hours using a non-additive S. A. E. grade 30 lubricating oil.

In the absence of dicyclohexyl nitrosamine in the fuel, deposits on the spark plug caused fouling thereof, necessitating engine shutdown, within hours after commencement of engine operation. A heavy reddish-yellow deposit was observed on the piston crown and combustion chamber head, and oil consumption average 0.30 pound per hour. With the gasoline containing dicyclohexyl nitrosamine no spark plug fouling was observed overthe entire period of the 50 hour test, piston and combustion chamber de posits were greatly decreased and were changed to a smooth character, and oil consumption was reduced to an average of 0.21 pound per hour.

Example II Example I was repeated using an S. A. E. grade lubricating oil containing 0.25% by weight as the sulfate ash, and 0.05% by weight of the calcium salts of oil soluble petroleum sulfonlc acids, calculated as the sulfate ash.

In the absence of dicyclohexyl nitrosamine in the fuel, deposits on the spark plug caused fouling thereof, necessitating engine shutdown, within 7 hours after commencement of engine operation, a heavy rough deposit was observed on the piston crown and combustion chamber head, and oil consumption averaged 0.41 pound per hour, whereas with the gasoline containing 0.02% by weight of dicyclohexyl nitrosamine no spark plug fouling was observed over the entire period of the 50 hour test, deposition was greatly reduced and was changed to a smooth character, and oil consumption was reduced to an average of 0.21 pound per hour.

Example III Example I is repeated except that diisopropyl nitrosamine is substituted for dicyclohexyl nitrosamine as the gasoline additive. When this gasoline composition is compared to the same gasoline without the diisopropyl nitrosamine, the results of Example I are substantially duplicated, i. e., by the incorporation of diisopropyl nitrosamine in the gasoline a significant increas in the period of engine operation before spark plug fouling necessitates a shutdown, a decrease in combustion chamber deposition, and a decrease in oil consumption is observed.

Example IV.

Example I is repeated except that N-nitroso diphenylamine is substituted for dicyclohexyl nitrosamine as the gasoline additive. This gasoline composition, when compared to the same gasoline without the N-nitroso diphenylamine under the operating conditions described in Example I, gives substantially identical results as described therein for dicyclohexyl nitrosamine, namely, a substantial increase in the length of engine operation before spark plug fouling, a decrease in combustion chamber deposition, and a decrease in oil consumption.

Other additives which have a nitroso group attached to a nitrogen atom which in turn is attached to an organic radical, as defined and illustrated hereinbefore, may be substituted in the above examples for the various nitrosamines therein employed, which latter nitrosamine'reppresents preferred materials selected to illustrate the present invention, and under substantially the same operating conditions results comparable to those described in the above examples are obtained.

In the above examples. a, significant and unobvious advantage obtained by engine operation in accordance with the present invention is the decrease in deposition in spark ignition engines operating on leaded fuels, and in the decrease in oil consumption by the operation of such engines, as demonstrated in the above examples. A further advantage is the change in properties of the combustion chamber deposits from a rough, hard, and uneven deposit to a soft, smooth de osit, caused by the presence in the gasoline of an additive containing a nitroso group attached to an organic radical through a nitrogen atom. This latter effect isof considerable importance. Thus, the hard deposit tends to become fused, heated to red heat, and by retaining the heat through the engine cycle .tends to cause pre-ignition of'the fuel in the subsequent cycles, whereas the soft deposit does not so tend to cause pre-ignition.

The foregoing examples demonstrate the surprising reduction of combustion chamber de-. posits, among the other advantages, obtained in accordance with the present invention, by incorporating into fuels for internal combustion engines only relatively small amounts of compounds having a nitroso group attached to a nitrogen atom which in turn is attached to an organic radical. The .use of the present fuel compositions in the operation of internal combustion engines constitutes a new process for the operation thereof, which process is within the scope of the present invention.

The present application is a continuation-inpart of the copending application Serial No. 690,068, filed August 12, 1946.

We claim as our invention:

1. A gasoline fuel for spark ignition internal combustion engines comprising a leaded mixture of gasoline hydrocarbons boiling from about 100 F. to about 400 F. and from about 0.01% to about 0.3% by weight of dicyclohexyl nitrosamine.

2. A gasoline fuel for spark ignition internal combustion engines comprising a leaded mixture of gasoline hydrocarbons boiling from about 100 F. to about 400 F. and from about 0.001% to about 1% trosamine.

3. A gasoline fuel for spark ignition internal combustion-engines comprising a leaded mixture of gasoline hydrocarbons boiling from about 100 F. to about 400 F. and from about 0.01% to about 0.3% by weight of diisopropyl nitrosamine.

4. A gasoline fuel for spark ignition internal combustion engines comprising a leaded mixture of gasoline hydrocarbons boiling from about 100 40 F. to about 400 about 1% F. and from about 0.001% to by weight of dilsopropyl nitrosamine.

by weight of dicyclo hexyl ni- 5. A gasoline fuel for spark ignition internal combustion engines comprising a leaded mixture of gasoline hydrocarbons boiling from about F. to about 400 F. and from about 0.01% to about 0.3% by weight of diphenyl nitrosamine.

6. A gasoline fuel comprising a leaded mixture of gasoline hydrocarbons and from about 0.01% to about 0.3% by weight of a compound having the formula wherein R1 and R2 are hydrocarbon radicals having together a total of from 6 to about 20 carbon atoms.

7. A gasoline fuel comprising a leaded mixture of gasoline hydrocarbons and from about 0.001% to about 1% by weight of an N-nitroso di(aliphatic hydrocarbon) secondary amine containing a total of from 6 to about 20 carbon atoms.

8. A gasoline fuel comprising a leaded mixture of gasoline hydrocarbons and from about 0.001% to about 1% by weight of an N-nitroso di(saturated hydrocarbon) secondary amine containing a total of from 6 to about 20 carbon atoms.

AARON WACHTER. NATHAN STILLMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,982,277 Winning Nov. 27, 1934 2,109,164 Clifford Feb. 22, 1938 FOREIGN PATENTS Number Country Date 323,463 Great Britain Dec. 27, 1929 

7. A GASOLINE FUEL COMPRISING A LEADED MIXTURE OF GASOLINE HYDROCARBONS AND FROM ABOUT 0.001% TO ABOUT 1% BY WEIGHT OF AN N-NITROSO DI(ALIPHATIC HYDROCARBON) SECONDARY AMINE CONTAINING A TOTAL OF FROM 6 TO ABOUT 20 CARBON ATOMS. 